Tuesday, June 25, 2013

In Your Face Geology

 En Route, Wisconsin

We are on the road again after a wonderful weekend with Sharon and Darrick.  Thank you so much Y-knot, we had a wonderful time.

Here is a subject, I've been holding back on:

When I was a lad in school, I was never interested in geology as something to study. Later in life also geology was not very interesting. But when we travel in the North American West geology is so much in your face that you can't ignore it. As you marvel at the natural wonders, you can't help wonder, "how did this come to be?"

For example, approaching San Diego from the east, you pass through California's Imperial Valley. Then suddenly you come to a swath of brilliant white sand and huge sand dunes. After after a few miles, the dunes and sand disappear behind you. How the heck...?

Next you come to a series of mountains that appear to be composed of 100% loose rubble and sand. The sides are very steep. How can they avoid being shaken nearly flat during earthquakes. What I expect is to see bald base rock at the summit of a mountain with rubble around the base. Indeed, most mountains are like that, but not all.

Speaking of summits, a lake in the Mohave Desert taught me something about the mountains in New York and Vermont. I was marveling over the fact that desert environment seemed to extend down the shores of this lake all the way to the surface. I expected a ring of green for at least a fewfeet from the surface because the capillary effect would suck the water up. Evidently the sandy soils of The West do not have the same capillary force as clay-like soils in The East. But then I thought about eastern mountains. The soil on the mountain sides can't suck the water up from the base, they must impede water from flowing down from above. Aha, I thought, that is probably why most of the mountain summits in The East are bald. At the very top, there is next no source of water seeping down from above. There is an are near the top that can not support plants.

We love thinking of theories to explain what we see. On highway 89 from Flagstaff, Arizona to Page,the road parallels a spectacular series of ridges. The area is known for volcanism and earthquakes. I was always sure that these ridges were thrust faults. I tried to envision being there to seethe earth split during an earthquake, and seeing the ground on one side of the fault thrust upward relative to the other. But in the weeks following, we saw several similar looking features. One of them was described as being formed by erosion. That casts doubt on our amateur geology theories for everything. Being right is not the point, having fun speculating is the point.

The same thing happened at Capitol Hill, near The Waterbreak Fold. Looking at the angle of exposed layers of rock we noticed some places with layers perpendicular to the cliffs, others more parallel. The angles didn't fit my theories. Finally, I realized that areas stretched by folding (the outside of the curves) might erode differently than those areas compressed (the inside of curves). Oh dear, it was much more complicated than I first thought.

Perhaps after this trip, we an find a good online video university course on geology. Other online university courses have been very enjoyable.

Sometime soon, I'll post a special photo essay on the geology we saw.

As I expect, bare bedrock on top and rubble on the bottom.  

No comments:

Post a Comment

Type your comments here.